Moving coil instrument with rotary permanent magnets



' April 16, 1968 H. HAUTMANN 3,378,768

MOVING COIL INSTRUMENT WITH ROTARY PERMANENT MAGNETS Filed July 6, 1964 l/V VE/V T02 /P/Cl/ HA UTMANA/ United States Patent 3,378,768 MOVING COIL INSTRUMENT WITH ROTARY PERMANENT MAGNETS Heinrich Hautmann, Erlangen, Bavaria, Germany, as-

signor to P. Gossen & Co., G.m.h.H., Erlangen, Ba-

varia, Germany, a firm Filed July 6, 1964, Ser. No. 380,538 Claims. (Cl. 324-150) ABSTRACT OF THE DISCLOSURE A moving coil instrument which has rotary permanent magnets. A pair of the latter magnets are provided. An outer pole piece, which has a supporting base plate, is formed with a pair of opposed magnet-receiving recesses extending at one end from the base plate. An inner, independent pole piece has an integral annular core and is, in part, surrounded by the outer pole piece and supported on the base plate of the latter, this inner pole piece having a pair of opposed recesses respectively directed toward the opposed recesses of the outer pole pieces and defining therewiith a pair of receiving spaces in which the permanent magnets are respectively received with these magnets resting on the supporting base plate of the outer pole piece. A coil is mounted on the inner pole piece for rotation around the core thereof and a retainer spring engages the permanent magnets for urging them toward the base plate of the outer pole piece while retaining the permanent magnets in the receiving spaces, respectively. The retainer spring, the inner pole piece, and the base plate of the outer pole piece are respectively formed with aligned apertures, and a single fastening screw extends through these aligned apertures for securing together the retainer spring, the inner pole piece, and the outer pole piece, while the permanent magnets are supported on the base plate for rotary adjusting movement.

This invention relates to measuring instruments or meters of the moving coil type, and in particular to such I instruments wherein the coil is movable over a recording range of approximately two hundred and seventy degrees. The basic principles of a moving coil meter are known. It is also known to mount a rotary coil so that it rotates around an annular core over a recording range of approximately two hundred and seventy degrees. However, prior art instruments of this type have required complex construction techniques, with the attendant increase in costs. Moreover, it is not possible to vary the sensitivity and characteristics of the prior art meters with ease.

Accordingly, an object of this invention is to provide a moving coil type meter which is relatively simple to construct.

Another object of the invention is to provide a moving coil type meter wherein the senstivity and characteristics of the instrument may be easily adjusted.

Briefly, the above objects are accomplished by subdividing the measuring instrument into two premanufactured pole piece assemblies having cooperating retainer portions into which the permanent magnets may be easily inserted. The pole pieces, with the magnets, may then be secured together by means of a screw, and the magnets properly magnetized in a conventional manner. As a further feature of the invention, the magnets are so held in the assembled construction that they can be adjusted after they are magnetized to alter the sensitivity and indicating characteristics of the instrument.

The manner in which the above and other objects of the invention are accomplished will be described in greater detail below with reference to the following drawings, wherein:

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FIGURE 1 is a top elevational view of the assembled meter;

FIGURE 2 is a top elevational view of the inner pole piece and coil assembly mounted thereon;

FIGURE 3 is a side view partially in section along the line 3--3 of FIGURE 2; and

FIGURE 4 is an exploded perspective view of the complete meter.

According to the invention, the measuring instrument includes an outer pole piece 10 and a cooperating inner pole piece 12. Both pole pieces may be readily fabricated or promanufactured prior to assembly of complete instrument. Outer pole piece 10 is made of a plurality of soft iron laminations 14 sandwiched between a similarly shaped upper sheet 16 and a bottom or base sheet or plate 18, the latter having a generally triangular configuration. Sheets 16 and 18 are both made of a nonmagnetic material. A round receiving aperture 20 extends vertically through the entire pole piece 10 to accommodate a portion of inner pole piece 12 as explained below.

The outer pole piece 10 includes opposing magnet receiving recesses 24 and 26 extending through laminations 16 and 14, and associated magnet adjustment apertures 28 and 30 in base sheet 18. Sheet 18 also includes an assembly guide hole 32 and external slot: 34, the purpose of which is described below, and a threaded aperture 36 used to secure the meter parts together.

The inner pole piece 12 is made of a plurality of soft iron laminations 38 secured between dissimilarly shaped upper and lower sheets 40 and 42, respectively. In the case of both laminated pole piece constructions, the individual sheets may be held together by and conventional means (not shown) such as bolts or the like. Of course the central portions of the pole pieces may be made of solid metal instead of laminated sheets.

Inner pole piece 12 includes a pair of magnet retaining recesses 44 and 46 which cooperate with outer pole recesses 24 and 26, respectively, to provide receiving spaces or seats for a pair of cylindrical permanent mag nets 43 and 50. Magnets 48 and 50 provide the magnetic field with which the field produced by the signal to be measured reacts, and include bottom grooves 49 and 51, respectively, for adjustment purposes as explained below. A vertical bore 52 coincides with the securing aperture 36 of outer pole piece .10 when the parts of the meter are properly assembled. Additionally, a pair of guide pins 54 and 56 extend downwardly from bottom sheet 42 into a cooperative relationship with assembly guide hole 32 and slot 34, respectively, in the base sheet 18 of the outer pole piece. The soft iron laminations 38 extend into an annular core 58 having a small opening which is closed by a suitably shaped soft iron pin 59 ina known manner to pro vide a constant magnetic field. Upper sheet 40 includes a large hook shaped portion 61 with a bent, inwardly extending mounting portion integrally formed therewith. Mounting portion 60 cooperates with an oppositely bent tab 62 extending from bottom sheet 42 to .rotatably support a conventional coil assembly 64 for rotation around annular core 58.

Coil assembly 64 is rectangular in cross section and includes opposing oifset pins 66 and 68 (FIGURE 3) which are received in conventional bearings 70 and 72, respectively, seated in mounting portions 60 and 62. Two conventional flat, coiled return springs (not shown) are soldered to respective thin, generally U-s=haped clips 71 and 73 positioned around mounting portion 60' and tab 62. The other ends of the return springs are electrically connected to opposite ends of the coil assembly 64 in a known fashion whereby bearings 76 and 72 may be utilized as the input terminals to which the signal to be measured is applied. This construction :functions as a spring mounting arrangement for the rotatable coil assembly, a feature which is also known in the prior art. The specific details of the coil mounting arrangement are conventional and therefore are not described further herein. The rotation of coil assembly 64 around annular core 58 is limited in each direction by abutment of the coil against suitable stop members which, for purposes of clarity, have been omitted from the drawings.

An indicator pin 76 is secured to coil assembly 64 to indicate the magnitude of the quantity being measured, which, of course, determines the magnetic field produced by coil assembly 64- and thus the force exerted on the rotatable assembly by magnets 48 and 55 A screw 89 passes through an aperture 84 of an elongated retainer spring 32 to threadedly engage aperture 36 of bottom sheet 18. In this manner the inner pole piece 12 and perm'anent magnets 48, 50 are securely held within outer pole piece 10.

The structure described above permits a remarkably simplified construction of the actual meter. Additionally,

after the meter has been assembled it is a simple matter to adjust the angular position of the magnets in order to vary the meter sensitivity and indicator characteristics.

To assemble the parts the meter, pin 59 is removed from annular core 58. Coil assembly 64 (with indicator pin 76) is inserted through the opening thus formed and positioned around the core as illustrated. Thereafter the coil is suitably journalled in a known manner in extensions 60 and 62, and pin 59 replaced in core 58. Inner pole piece 12 is then placed in pole piece 1%- with guide pins 54 and 56 being inserted into guide aperture 32 and slot 34, respectively. Permanent magnets 48 and 50, prior to magnetization, are pushed into their respective seats, the retainer spring 82 applied, and screw 80 inserted through aperture 84, bore 52 and threaded aperture 36. The screw is then tightened to secure the various parts together.

After assembly, the entire meter construction is placed in a magnetizing device schematically illustrated in FIG- URE 1 as comprising south poles 9t and 92 and north pole 94. Such devices are known and function to create the indicated poles in the permanent magnets 48 and 50. If it is then desirable to adjust the meter sensitivity or characteristics, a screw driver may be inserted into grooves 49 or 51 through openings 28 or 30, and the magnets adjusted to a desired position. To prevent further undesired rotation of the magnets they are held in their preferred position by an adhesive such as glue.

Although a preferred embodiment of the invention has been illustrated and described, many modifications thereof will be obvious to those skilled in the art and the invention should not be limited except as defined in the following claims.

What is claimed is: v

1. A moving coil instrument, comprising a pair of permanent magnets, an outer pole piece having a base plate and formed with a pair of opposed recesses extending at one end from said base plate, an inner pole piece having an integral annular core, supported by said base plate, and being formed with a pair of opposed recesses respectively directed toward said opposed recesses of said outer pole piece and defining therewith a pair of magnetreceiving spaces in which said pair of permanent magnets are respectively located with said latter magnets resting on said base plate, a coil mounted on said inner pole piece for rotation around said core, a retainer spring engaging said permanent magnets for urging the latter toward said base plate, said spring, said inner pole piece, and said base plate of said outer pole piece all being respectively formed with aligned openings passing therethrough, and a single screw fastener extending through said aligned openings for securing together said outer pole piece, said inner pole piece and said permanent magnets.

2. A measuring instrument according to claim 1, wherein said permanent magnets are cylindrical and said recesses form parts of cylinders.

3. A measuring instrument according to claim 2, wherein one of said pole pieces includes guide pins cooperating with corresponding apertures in the other of said pole pieces.

4. A measuring instrument according to claim 3, wherein said magnets are respectively formed at their end faces which engage said base plate with transverse grooves, and said base plate being formed with apertures through which said grooves are accessible for facilitating rotary movement of said magnets with respect to said base plate.

5. A measuring instrument according to claim 4, wherein said inner pole piece includes mounting tabs above and below said annular core, said coil being pivotally mounted on said mounting tabs.

References titted UNITED STATES PATENTS 1,976,498 10/1934 Hoare et al 324-150 2,3 67,950 1/ 1945 Lenehan 324-150 2,832,932 4/1958 Baerman 324152 3,111,623 8/1958 Thomander 324-150 3,139,581 6/1964 Berger 324 150 FOREIGN PATENTS 456,988 11/1936 Great Britain.

RUDOLPH V. ROLINEC, Primary Examiner.

P. A. URIBE, Assistant Examiner. 

